"Nothing happens by accident in a supermarket. Everything is designed to sell."

And that, says Consumer Reports (http://www.consumerreports.org/) retail expert Tod Marks, is the key thing to keep in mind as you go up and down the aisles of your local store. Knowing how to shop is vital.

Supermarkets "are in the real estate business," Marks pointed out to Early Show consumer correspondent Susan Koeppen Monday in the first of her three-part series, "Supermarket Secrets."